Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * auth-scram.c
4 : * Server-side implementation of the SASL SCRAM-SHA-256 mechanism.
5 : *
6 : * See the following RFCs for more details:
7 : * - RFC 5802: https://tools.ietf.org/html/rfc5802
8 : * - RFC 5803: https://tools.ietf.org/html/rfc5803
9 : * - RFC 7677: https://tools.ietf.org/html/rfc7677
10 : *
11 : * Here are some differences:
12 : *
13 : * - Username from the authentication exchange is not used. The client
14 : * should send an empty string as the username.
15 : *
16 : * - If the password isn't valid UTF-8, or contains characters prohibited
17 : * by the SASLprep profile, we skip the SASLprep pre-processing and use
18 : * the raw bytes in calculating the hash.
19 : *
20 : * - If channel binding is used, the channel binding type is always
21 : * "tls-server-end-point". The spec says the default is "tls-unique"
22 : * (RFC 5802, section 6.1. Default Channel Binding), but there are some
23 : * problems with that. Firstly, not all SSL libraries provide an API to
24 : * get the TLS Finished message, required to use "tls-unique". Secondly,
25 : * "tls-unique" is not specified for TLS v1.3, and as of this writing,
26 : * it's not clear if there will be a replacement. We could support both
27 : * "tls-server-end-point" and "tls-unique", but for our use case,
28 : * "tls-unique" doesn't really have any advantages. The main advantage
29 : * of "tls-unique" would be that it works even if the server doesn't
30 : * have a certificate, but PostgreSQL requires a server certificate
31 : * whenever SSL is used, anyway.
32 : *
33 : *
34 : * The password stored in pg_authid consists of the iteration count, salt,
35 : * StoredKey and ServerKey.
36 : *
37 : * SASLprep usage
38 : * --------------
39 : *
40 : * One notable difference to the SCRAM specification is that while the
41 : * specification dictates that the password is in UTF-8, and prohibits
42 : * certain characters, we are more lenient. If the password isn't a valid
43 : * UTF-8 string, or contains prohibited characters, the raw bytes are used
44 : * to calculate the hash instead, without SASLprep processing. This is
45 : * because PostgreSQL supports other encodings too, and the encoding being
46 : * used during authentication is undefined (client_encoding isn't set until
47 : * after authentication). In effect, we try to interpret the password as
48 : * UTF-8 and apply SASLprep processing, but if it looks invalid, we assume
49 : * that it's in some other encoding.
50 : *
51 : * In the worst case, we misinterpret a password that's in a different
52 : * encoding as being Unicode, because it happens to consists entirely of
53 : * valid UTF-8 bytes, and we apply Unicode normalization to it. As long
54 : * as we do that consistently, that will not lead to failed logins.
55 : * Fortunately, the UTF-8 byte sequences that are ignored by SASLprep
56 : * don't correspond to any commonly used characters in any of the other
57 : * supported encodings, so it should not lead to any significant loss in
58 : * entropy, even if the normalization is incorrectly applied to a
59 : * non-UTF-8 password.
60 : *
61 : * Error handling
62 : * --------------
63 : *
64 : * Don't reveal user information to an unauthenticated client. We don't
65 : * want an attacker to be able to probe whether a particular username is
66 : * valid. In SCRAM, the server has to read the salt and iteration count
67 : * from the user's stored secret, and send it to the client. To avoid
68 : * revealing whether a user exists, when the client tries to authenticate
69 : * with a username that doesn't exist, or doesn't have a valid SCRAM
70 : * secret in pg_authid, we create a fake salt and iteration count
71 : * on-the-fly, and proceed with the authentication with that. In the end,
72 : * we'll reject the attempt, as if an incorrect password was given. When
73 : * we are performing a "mock" authentication, the 'doomed' flag in
74 : * scram_state is set.
75 : *
76 : * In the error messages, avoid printing strings from the client, unless
77 : * you check that they are pure ASCII. We don't want an unauthenticated
78 : * attacker to be able to spam the logs with characters that are not valid
79 : * to the encoding being used, whatever that is. We cannot avoid that in
80 : * general, after logging in, but let's do what we can here.
81 : *
82 : *
83 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
84 : * Portions Copyright (c) 1994, Regents of the University of California
85 : *
86 : * src/backend/libpq/auth-scram.c
87 : *
88 : *-------------------------------------------------------------------------
89 : */
90 : #include "postgres.h"
91 :
92 : #include <unistd.h>
93 :
94 : #include "access/xlog.h"
95 : #include "catalog/pg_control.h"
96 : #include "common/base64.h"
97 : #include "common/hmac.h"
98 : #include "common/saslprep.h"
99 : #include "common/scram-common.h"
100 : #include "common/sha2.h"
101 : #include "libpq/crypt.h"
102 : #include "libpq/sasl.h"
103 : #include "libpq/scram.h"
104 : #include "miscadmin.h"
105 :
106 : static void scram_get_mechanisms(Port *port, StringInfo buf);
107 : static void *scram_init(Port *port, const char *selected_mech,
108 : const char *shadow_pass);
109 : static int scram_exchange(void *opaq, const char *input, int inputlen,
110 : char **output, int *outputlen,
111 : const char **logdetail);
112 :
113 : /* Mechanism declaration */
114 : const pg_be_sasl_mech pg_be_scram_mech = {
115 : scram_get_mechanisms,
116 : scram_init,
117 : scram_exchange,
118 :
119 : PG_MAX_SASL_MESSAGE_LENGTH
120 : };
121 :
122 : /*
123 : * Status data for a SCRAM authentication exchange. This should be kept
124 : * internal to this file.
125 : */
126 : typedef enum
127 : {
128 : SCRAM_AUTH_INIT,
129 : SCRAM_AUTH_SALT_SENT,
130 : SCRAM_AUTH_FINISHED,
131 : } scram_state_enum;
132 :
133 : typedef struct
134 : {
135 : scram_state_enum state;
136 :
137 : const char *username; /* username from startup packet */
138 :
139 : Port *port;
140 : bool channel_binding_in_use;
141 :
142 : /* State data depending on the hash type */
143 : pg_cryptohash_type hash_type;
144 : int key_length;
145 :
146 : int iterations;
147 : char *salt; /* base64-encoded */
148 : uint8 ClientKey[SCRAM_MAX_KEY_LEN];
149 : uint8 StoredKey[SCRAM_MAX_KEY_LEN];
150 : uint8 ServerKey[SCRAM_MAX_KEY_LEN];
151 :
152 : /* Fields of the first message from client */
153 : char cbind_flag;
154 : char *client_first_message_bare;
155 : char *client_username;
156 : char *client_nonce;
157 :
158 : /* Fields from the last message from client */
159 : char *client_final_message_without_proof;
160 : char *client_final_nonce;
161 : char ClientProof[SCRAM_MAX_KEY_LEN];
162 :
163 : /* Fields generated in the server */
164 : char *server_first_message;
165 : char *server_nonce;
166 :
167 : /*
168 : * If something goes wrong during the authentication, or we are performing
169 : * a "mock" authentication (see comments at top of file), the 'doomed'
170 : * flag is set. A reason for the failure, for the server log, is put in
171 : * 'logdetail'.
172 : */
173 : bool doomed;
174 : char *logdetail;
175 : } scram_state;
176 :
177 : static void read_client_first_message(scram_state *state, const char *input);
178 : static void read_client_final_message(scram_state *state, const char *input);
179 : static char *build_server_first_message(scram_state *state);
180 : static char *build_server_final_message(scram_state *state);
181 : static bool verify_client_proof(scram_state *state);
182 : static bool verify_final_nonce(scram_state *state);
183 : static void mock_scram_secret(const char *username, pg_cryptohash_type *hash_type,
184 : int *iterations, int *key_length, char **salt,
185 : uint8 *stored_key, uint8 *server_key);
186 : static bool is_scram_printable(char *p);
187 : static char *sanitize_char(char c);
188 : static char *sanitize_str(const char *s);
189 : static char *scram_mock_salt(const char *username,
190 : pg_cryptohash_type hash_type,
191 : int key_length);
192 :
193 : /*
194 : * The number of iterations to use when generating new secrets.
195 : */
196 : int scram_sha_256_iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
197 :
198 : /*
199 : * Get a list of SASL mechanisms that this module supports.
200 : *
201 : * For the convenience of building the FE/BE packet that lists the
202 : * mechanisms, the names are appended to the given StringInfo buffer,
203 : * separated by '\0' bytes.
204 : */
205 : static void
206 118 : scram_get_mechanisms(Port *port, StringInfo buf)
207 : {
208 : /*
209 : * Advertise the mechanisms in decreasing order of importance. So the
210 : * channel-binding variants go first, if they are supported. Channel
211 : * binding is only supported with SSL.
212 : */
213 : #ifdef USE_SSL
214 118 : if (port->ssl_in_use)
215 : {
216 14 : appendStringInfoString(buf, SCRAM_SHA_256_PLUS_NAME);
217 14 : appendStringInfoChar(buf, '\0');
218 : }
219 : #endif
220 118 : appendStringInfoString(buf, SCRAM_SHA_256_NAME);
221 118 : appendStringInfoChar(buf, '\0');
222 118 : }
223 :
224 : /*
225 : * Initialize a new SCRAM authentication exchange status tracker. This
226 : * needs to be called before doing any exchange. It will be filled later
227 : * after the beginning of the exchange with authentication information.
228 : *
229 : * 'selected_mech' identifies the SASL mechanism that the client selected.
230 : * It should be one of the mechanisms that we support, as returned by
231 : * scram_get_mechanisms().
232 : *
233 : * 'shadow_pass' is the role's stored secret, from pg_authid.rolpassword.
234 : * The username was provided by the client in the startup message, and is
235 : * available in port->user_name. If 'shadow_pass' is NULL, we still perform
236 : * an authentication exchange, but it will fail, as if an incorrect password
237 : * was given.
238 : */
239 : static void *
240 96 : scram_init(Port *port, const char *selected_mech, const char *shadow_pass)
241 : {
242 : scram_state *state;
243 : bool got_secret;
244 :
245 96 : state = (scram_state *) palloc0(sizeof(scram_state));
246 96 : state->port = port;
247 96 : state->state = SCRAM_AUTH_INIT;
248 :
249 : /*
250 : * Parse the selected mechanism.
251 : *
252 : * Note that if we don't support channel binding, or if we're not using
253 : * SSL at all, we would not have advertised the PLUS variant in the first
254 : * place. If the client nevertheless tries to select it, it's a protocol
255 : * violation like selecting any other SASL mechanism we don't support.
256 : */
257 : #ifdef USE_SSL
258 96 : if (strcmp(selected_mech, SCRAM_SHA_256_PLUS_NAME) == 0 && port->ssl_in_use)
259 10 : state->channel_binding_in_use = true;
260 : else
261 : #endif
262 86 : if (strcmp(selected_mech, SCRAM_SHA_256_NAME) == 0)
263 86 : state->channel_binding_in_use = false;
264 : else
265 0 : ereport(ERROR,
266 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
267 : errmsg("client selected an invalid SASL authentication mechanism")));
268 :
269 : /*
270 : * Parse the stored secret.
271 : */
272 96 : if (shadow_pass)
273 : {
274 96 : int password_type = get_password_type(shadow_pass);
275 :
276 96 : if (password_type == PASSWORD_TYPE_SCRAM_SHA_256)
277 : {
278 94 : if (parse_scram_secret(shadow_pass, &state->iterations,
279 : &state->hash_type, &state->key_length,
280 : &state->salt,
281 94 : state->StoredKey,
282 94 : state->ServerKey))
283 94 : got_secret = true;
284 : else
285 : {
286 : /*
287 : * The password looked like a SCRAM secret, but could not be
288 : * parsed.
289 : */
290 0 : ereport(LOG,
291 : (errmsg("invalid SCRAM secret for user \"%s\"",
292 : state->port->user_name)));
293 0 : got_secret = false;
294 : }
295 : }
296 : else
297 : {
298 : /*
299 : * The user doesn't have SCRAM secret. (You cannot do SCRAM
300 : * authentication with an MD5 hash.)
301 : */
302 4 : state->logdetail = psprintf(_("User \"%s\" does not have a valid SCRAM secret."),
303 2 : state->port->user_name);
304 2 : got_secret = false;
305 : }
306 : }
307 : else
308 : {
309 : /*
310 : * The caller requested us to perform a dummy authentication. This is
311 : * considered normal, since the caller requested it, so don't set log
312 : * detail.
313 : */
314 0 : got_secret = false;
315 : }
316 :
317 : /*
318 : * If the user did not have a valid SCRAM secret, we still go through the
319 : * motions with a mock one, and fail as if the client supplied an
320 : * incorrect password. This is to avoid revealing information to an
321 : * attacker.
322 : */
323 96 : if (!got_secret)
324 : {
325 2 : mock_scram_secret(state->port->user_name, &state->hash_type,
326 : &state->iterations, &state->key_length,
327 : &state->salt,
328 2 : state->StoredKey, state->ServerKey);
329 2 : state->doomed = true;
330 : }
331 :
332 96 : return state;
333 : }
334 :
335 : /*
336 : * Continue a SCRAM authentication exchange.
337 : *
338 : * 'input' is the SCRAM payload sent by the client. On the first call,
339 : * 'input' contains the "Initial Client Response" that the client sent as
340 : * part of the SASLInitialResponse message, or NULL if no Initial Client
341 : * Response was given. (The SASL specification distinguishes between an
342 : * empty response and non-existing one.) On subsequent calls, 'input'
343 : * cannot be NULL. For convenience in this function, the caller must
344 : * ensure that there is a null terminator at input[inputlen].
345 : *
346 : * The next message to send to client is saved in 'output', for a length
347 : * of 'outputlen'. In the case of an error, optionally store a palloc'd
348 : * string at *logdetail that will be sent to the postmaster log (but not
349 : * the client).
350 : */
351 : static int
352 192 : scram_exchange(void *opaq, const char *input, int inputlen,
353 : char **output, int *outputlen, const char **logdetail)
354 : {
355 192 : scram_state *state = (scram_state *) opaq;
356 : int result;
357 :
358 192 : *output = NULL;
359 :
360 : /*
361 : * If the client didn't include an "Initial Client Response" in the
362 : * SASLInitialResponse message, send an empty challenge, to which the
363 : * client will respond with the same data that usually comes in the
364 : * Initial Client Response.
365 : */
366 192 : if (input == NULL)
367 : {
368 : Assert(state->state == SCRAM_AUTH_INIT);
369 :
370 0 : *output = pstrdup("");
371 0 : *outputlen = 0;
372 0 : return PG_SASL_EXCHANGE_CONTINUE;
373 : }
374 :
375 : /*
376 : * Check that the input length agrees with the string length of the input.
377 : * We can ignore inputlen after this.
378 : */
379 192 : if (inputlen == 0)
380 0 : ereport(ERROR,
381 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
382 : errmsg("malformed SCRAM message"),
383 : errdetail("The message is empty.")));
384 192 : if (inputlen != strlen(input))
385 0 : ereport(ERROR,
386 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
387 : errmsg("malformed SCRAM message"),
388 : errdetail("Message length does not match input length.")));
389 :
390 192 : switch (state->state)
391 : {
392 96 : case SCRAM_AUTH_INIT:
393 :
394 : /*
395 : * Initialization phase. Receive the first message from client
396 : * and be sure that it parsed correctly. Then send the challenge
397 : * to the client.
398 : */
399 96 : read_client_first_message(state, input);
400 :
401 : /* prepare message to send challenge */
402 96 : *output = build_server_first_message(state);
403 :
404 96 : state->state = SCRAM_AUTH_SALT_SENT;
405 96 : result = PG_SASL_EXCHANGE_CONTINUE;
406 96 : break;
407 :
408 96 : case SCRAM_AUTH_SALT_SENT:
409 :
410 : /*
411 : * Final phase for the server. Receive the response to the
412 : * challenge previously sent, verify, and let the client know that
413 : * everything went well (or not).
414 : */
415 96 : read_client_final_message(state, input);
416 :
417 96 : if (!verify_final_nonce(state))
418 0 : ereport(ERROR,
419 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
420 : errmsg("invalid SCRAM response"),
421 : errdetail("Nonce does not match.")));
422 :
423 : /*
424 : * Now check the final nonce and the client proof.
425 : *
426 : * If we performed a "mock" authentication that we knew would fail
427 : * from the get go, this is where we fail.
428 : *
429 : * The SCRAM specification includes an error code,
430 : * "invalid-proof", for authentication failure, but it also allows
431 : * erroring out in an application-specific way. We choose to do
432 : * the latter, so that the error message for invalid password is
433 : * the same for all authentication methods. The caller will call
434 : * ereport(), when we return PG_SASL_EXCHANGE_FAILURE with no
435 : * output.
436 : *
437 : * NB: the order of these checks is intentional. We calculate the
438 : * client proof even in a mock authentication, even though it's
439 : * bound to fail, to thwart timing attacks to determine if a role
440 : * with the given name exists or not.
441 : */
442 96 : if (!verify_client_proof(state) || state->doomed)
443 : {
444 10 : result = PG_SASL_EXCHANGE_FAILURE;
445 10 : break;
446 : }
447 :
448 : /* Build final message for client */
449 86 : *output = build_server_final_message(state);
450 :
451 : /* Success! */
452 86 : result = PG_SASL_EXCHANGE_SUCCESS;
453 86 : state->state = SCRAM_AUTH_FINISHED;
454 86 : break;
455 :
456 0 : default:
457 0 : elog(ERROR, "invalid SCRAM exchange state");
458 : result = PG_SASL_EXCHANGE_FAILURE;
459 : }
460 :
461 192 : if (result == PG_SASL_EXCHANGE_FAILURE && state->logdetail && logdetail)
462 2 : *logdetail = state->logdetail;
463 :
464 192 : if (*output)
465 182 : *outputlen = strlen(*output);
466 :
467 192 : if (result == PG_SASL_EXCHANGE_SUCCESS && state->state == SCRAM_AUTH_FINISHED)
468 : {
469 86 : memcpy(MyProcPort->scram_ClientKey, state->ClientKey, sizeof(MyProcPort->scram_ClientKey));
470 86 : memcpy(MyProcPort->scram_ServerKey, state->ServerKey, sizeof(MyProcPort->scram_ServerKey));
471 86 : MyProcPort->has_scram_keys = true;
472 : }
473 :
474 192 : return result;
475 : }
476 :
477 : /*
478 : * Construct a SCRAM secret, for storing in pg_authid.rolpassword.
479 : *
480 : * The result is palloc'd, so caller is responsible for freeing it.
481 : */
482 : char *
483 102 : pg_be_scram_build_secret(const char *password)
484 : {
485 : char *prep_password;
486 : pg_saslprep_rc rc;
487 : char saltbuf[SCRAM_DEFAULT_SALT_LEN];
488 : char *result;
489 102 : const char *errstr = NULL;
490 :
491 : /*
492 : * Normalize the password with SASLprep. If that doesn't work, because
493 : * the password isn't valid UTF-8 or contains prohibited characters, just
494 : * proceed with the original password. (See comments at top of file.)
495 : */
496 102 : rc = pg_saslprep(password, &prep_password);
497 102 : if (rc == SASLPREP_SUCCESS)
498 100 : password = (const char *) prep_password;
499 :
500 : /* Generate random salt */
501 102 : if (!pg_strong_random(saltbuf, SCRAM_DEFAULT_SALT_LEN))
502 0 : ereport(ERROR,
503 : (errcode(ERRCODE_INTERNAL_ERROR),
504 : errmsg("could not generate random salt")));
505 :
506 102 : result = scram_build_secret(PG_SHA256, SCRAM_SHA_256_KEY_LEN,
507 : saltbuf, SCRAM_DEFAULT_SALT_LEN,
508 : scram_sha_256_iterations, password,
509 : &errstr);
510 :
511 102 : if (prep_password)
512 100 : pfree(prep_password);
513 :
514 102 : return result;
515 : }
516 :
517 : /*
518 : * Verify a plaintext password against a SCRAM secret. This is used when
519 : * performing plaintext password authentication for a user that has a SCRAM
520 : * secret stored in pg_authid.
521 : */
522 : bool
523 52 : scram_verify_plain_password(const char *username, const char *password,
524 : const char *secret)
525 : {
526 : char *encoded_salt;
527 : char *salt;
528 : int saltlen;
529 : int iterations;
530 52 : int key_length = 0;
531 : pg_cryptohash_type hash_type;
532 : uint8 salted_password[SCRAM_MAX_KEY_LEN];
533 : uint8 stored_key[SCRAM_MAX_KEY_LEN];
534 : uint8 server_key[SCRAM_MAX_KEY_LEN];
535 : uint8 computed_key[SCRAM_MAX_KEY_LEN];
536 : char *prep_password;
537 : pg_saslprep_rc rc;
538 52 : const char *errstr = NULL;
539 :
540 52 : if (!parse_scram_secret(secret, &iterations, &hash_type, &key_length,
541 : &encoded_salt, stored_key, server_key))
542 : {
543 : /*
544 : * The password looked like a SCRAM secret, but could not be parsed.
545 : */
546 0 : ereport(LOG,
547 : (errmsg("invalid SCRAM secret for user \"%s\"", username)));
548 0 : return false;
549 : }
550 :
551 52 : saltlen = pg_b64_dec_len(strlen(encoded_salt));
552 52 : salt = palloc(saltlen);
553 52 : saltlen = pg_b64_decode(encoded_salt, strlen(encoded_salt), salt,
554 : saltlen);
555 52 : if (saltlen < 0)
556 : {
557 0 : ereport(LOG,
558 : (errmsg("invalid SCRAM secret for user \"%s\"", username)));
559 0 : return false;
560 : }
561 :
562 : /* Normalize the password */
563 52 : rc = pg_saslprep(password, &prep_password);
564 52 : if (rc == SASLPREP_SUCCESS)
565 52 : password = prep_password;
566 :
567 : /* Compute Server Key based on the user-supplied plaintext password */
568 52 : if (scram_SaltedPassword(password, hash_type, key_length,
569 : salt, saltlen, iterations,
570 52 : salted_password, &errstr) < 0 ||
571 52 : scram_ServerKey(salted_password, hash_type, key_length,
572 : computed_key, &errstr) < 0)
573 : {
574 0 : elog(ERROR, "could not compute server key: %s", errstr);
575 : }
576 :
577 52 : if (prep_password)
578 52 : pfree(prep_password);
579 :
580 : /*
581 : * Compare the secret's Server Key with the one computed from the
582 : * user-supplied password.
583 : */
584 52 : return memcmp(computed_key, server_key, key_length) == 0;
585 : }
586 :
587 :
588 : /*
589 : * Parse and validate format of given SCRAM secret.
590 : *
591 : * On success, the iteration count, salt, stored key, and server key are
592 : * extracted from the secret, and returned to the caller. For 'stored_key'
593 : * and 'server_key', the caller must pass pre-allocated buffers of size
594 : * SCRAM_MAX_KEY_LEN. Salt is returned as a base64-encoded, null-terminated
595 : * string. The buffer for the salt is palloc'd by this function.
596 : *
597 : * Returns true if the SCRAM secret has been parsed, and false otherwise.
598 : */
599 : bool
600 808 : parse_scram_secret(const char *secret, int *iterations,
601 : pg_cryptohash_type *hash_type, int *key_length,
602 : char **salt, uint8 *stored_key, uint8 *server_key)
603 : {
604 : char *v;
605 : char *p;
606 : char *scheme_str;
607 : char *salt_str;
608 : char *iterations_str;
609 : char *storedkey_str;
610 : char *serverkey_str;
611 : int decoded_len;
612 : char *decoded_salt_buf;
613 : char *decoded_stored_buf;
614 : char *decoded_server_buf;
615 :
616 : /*
617 : * The secret is of form:
618 : *
619 : * SCRAM-SHA-256$<iterations>:<salt>$<storedkey>:<serverkey>
620 : */
621 808 : v = pstrdup(secret);
622 808 : scheme_str = strsep(&v, "$");
623 808 : if (v == NULL)
624 222 : goto invalid_secret;
625 586 : iterations_str = strsep(&v, ":");
626 586 : if (v == NULL)
627 12 : goto invalid_secret;
628 574 : salt_str = strsep(&v, "$");
629 574 : if (v == NULL)
630 0 : goto invalid_secret;
631 574 : storedkey_str = strsep(&v, ":");
632 574 : if (v == NULL)
633 0 : goto invalid_secret;
634 574 : serverkey_str = v;
635 :
636 : /* Parse the fields */
637 574 : if (strcmp(scheme_str, "SCRAM-SHA-256") != 0)
638 0 : goto invalid_secret;
639 574 : *hash_type = PG_SHA256;
640 574 : *key_length = SCRAM_SHA_256_KEY_LEN;
641 :
642 574 : errno = 0;
643 574 : *iterations = strtol(iterations_str, &p, 10);
644 574 : if (*p || errno != 0)
645 0 : goto invalid_secret;
646 :
647 : /*
648 : * Verify that the salt is in Base64-encoded format, by decoding it,
649 : * although we return the encoded version to the caller.
650 : */
651 574 : decoded_len = pg_b64_dec_len(strlen(salt_str));
652 574 : decoded_salt_buf = palloc(decoded_len);
653 574 : decoded_len = pg_b64_decode(salt_str, strlen(salt_str),
654 : decoded_salt_buf, decoded_len);
655 574 : if (decoded_len < 0)
656 0 : goto invalid_secret;
657 574 : *salt = pstrdup(salt_str);
658 :
659 : /*
660 : * Decode StoredKey and ServerKey.
661 : */
662 574 : decoded_len = pg_b64_dec_len(strlen(storedkey_str));
663 574 : decoded_stored_buf = palloc(decoded_len);
664 574 : decoded_len = pg_b64_decode(storedkey_str, strlen(storedkey_str),
665 : decoded_stored_buf, decoded_len);
666 574 : if (decoded_len != *key_length)
667 12 : goto invalid_secret;
668 562 : memcpy(stored_key, decoded_stored_buf, *key_length);
669 :
670 562 : decoded_len = pg_b64_dec_len(strlen(serverkey_str));
671 562 : decoded_server_buf = palloc(decoded_len);
672 562 : decoded_len = pg_b64_decode(serverkey_str, strlen(serverkey_str),
673 : decoded_server_buf, decoded_len);
674 562 : if (decoded_len != *key_length)
675 12 : goto invalid_secret;
676 550 : memcpy(server_key, decoded_server_buf, *key_length);
677 :
678 550 : return true;
679 :
680 258 : invalid_secret:
681 258 : *salt = NULL;
682 258 : return false;
683 : }
684 :
685 : /*
686 : * Generate plausible SCRAM secret parameters for mock authentication.
687 : *
688 : * In a normal authentication, these are extracted from the secret
689 : * stored in the server. This function generates values that look
690 : * realistic, for when there is no stored secret, using SCRAM-SHA-256.
691 : *
692 : * Like in parse_scram_secret(), for 'stored_key' and 'server_key', the
693 : * caller must pass pre-allocated buffers of size SCRAM_MAX_KEY_LEN, and
694 : * the buffer for the salt is palloc'd by this function.
695 : */
696 : static void
697 2 : mock_scram_secret(const char *username, pg_cryptohash_type *hash_type,
698 : int *iterations, int *key_length, char **salt,
699 : uint8 *stored_key, uint8 *server_key)
700 : {
701 : char *raw_salt;
702 : char *encoded_salt;
703 : int encoded_len;
704 :
705 : /* Enforce the use of SHA-256, which would be realistic enough */
706 2 : *hash_type = PG_SHA256;
707 2 : *key_length = SCRAM_SHA_256_KEY_LEN;
708 :
709 : /*
710 : * Generate deterministic salt.
711 : *
712 : * Note that we cannot reveal any information to an attacker here so the
713 : * error messages need to remain generic. This should never fail anyway
714 : * as the salt generated for mock authentication uses the cluster's nonce
715 : * value.
716 : */
717 2 : raw_salt = scram_mock_salt(username, *hash_type, *key_length);
718 2 : if (raw_salt == NULL)
719 0 : elog(ERROR, "could not encode salt");
720 :
721 2 : encoded_len = pg_b64_enc_len(SCRAM_DEFAULT_SALT_LEN);
722 : /* don't forget the zero-terminator */
723 2 : encoded_salt = (char *) palloc(encoded_len + 1);
724 2 : encoded_len = pg_b64_encode(raw_salt, SCRAM_DEFAULT_SALT_LEN, encoded_salt,
725 : encoded_len);
726 :
727 2 : if (encoded_len < 0)
728 0 : elog(ERROR, "could not encode salt");
729 2 : encoded_salt[encoded_len] = '\0';
730 :
731 2 : *salt = encoded_salt;
732 2 : *iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
733 :
734 : /* StoredKey and ServerKey are not used in a doomed authentication */
735 2 : memset(stored_key, 0, SCRAM_MAX_KEY_LEN);
736 2 : memset(server_key, 0, SCRAM_MAX_KEY_LEN);
737 2 : }
738 :
739 : /*
740 : * Read the value in a given SCRAM exchange message for given attribute.
741 : */
742 : static char *
743 394 : read_attr_value(char **input, char attr)
744 : {
745 394 : char *begin = *input;
746 : char *end;
747 :
748 394 : if (*begin != attr)
749 0 : ereport(ERROR,
750 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
751 : errmsg("malformed SCRAM message"),
752 : errdetail("Expected attribute \"%c\" but found \"%s\".",
753 : attr, sanitize_char(*begin))));
754 394 : begin++;
755 :
756 394 : if (*begin != '=')
757 0 : ereport(ERROR,
758 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
759 : errmsg("malformed SCRAM message"),
760 : errdetail("Expected character \"=\" for attribute \"%c\".", attr)));
761 394 : begin++;
762 :
763 394 : end = begin;
764 8610 : while (*end && *end != ',')
765 8216 : end++;
766 :
767 394 : if (*end)
768 : {
769 298 : *end = '\0';
770 298 : *input = end + 1;
771 : }
772 : else
773 96 : *input = end;
774 :
775 394 : return begin;
776 : }
777 :
778 : static bool
779 96 : is_scram_printable(char *p)
780 : {
781 : /*------
782 : * Printable characters, as defined by SCRAM spec: (RFC 5802)
783 : *
784 : * printable = %x21-2B / %x2D-7E
785 : * ;; Printable ASCII except ",".
786 : * ;; Note that any "printable" is also
787 : * ;; a valid "value".
788 : *------
789 : */
790 2400 : for (; *p; p++)
791 : {
792 2304 : if (*p < 0x21 || *p > 0x7E || *p == 0x2C /* comma */ )
793 0 : return false;
794 : }
795 96 : return true;
796 : }
797 :
798 : /*
799 : * Convert an arbitrary byte to printable form. For error messages.
800 : *
801 : * If it's a printable ASCII character, print it as a single character.
802 : * otherwise, print it in hex.
803 : *
804 : * The returned pointer points to a static buffer.
805 : */
806 : static char *
807 0 : sanitize_char(char c)
808 : {
809 : static char buf[5];
810 :
811 0 : if (c >= 0x21 && c <= 0x7E)
812 0 : snprintf(buf, sizeof(buf), "'%c'", c);
813 : else
814 0 : snprintf(buf, sizeof(buf), "0x%02x", (unsigned char) c);
815 0 : return buf;
816 : }
817 :
818 : /*
819 : * Convert an arbitrary string to printable form, for error messages.
820 : *
821 : * Anything that's not a printable ASCII character is replaced with
822 : * '?', and the string is truncated at 30 characters.
823 : *
824 : * The returned pointer points to a static buffer.
825 : */
826 : static char *
827 0 : sanitize_str(const char *s)
828 : {
829 : static char buf[30 + 1];
830 : int i;
831 :
832 0 : for (i = 0; i < sizeof(buf) - 1; i++)
833 : {
834 0 : char c = s[i];
835 :
836 0 : if (c == '\0')
837 0 : break;
838 :
839 0 : if (c >= 0x21 && c <= 0x7E)
840 0 : buf[i] = c;
841 : else
842 0 : buf[i] = '?';
843 : }
844 0 : buf[i] = '\0';
845 0 : return buf;
846 : }
847 :
848 : /*
849 : * Read the next attribute and value in a SCRAM exchange message.
850 : *
851 : * The attribute character is set in *attr_p, the attribute value is the
852 : * return value.
853 : */
854 : static char *
855 96 : read_any_attr(char **input, char *attr_p)
856 : {
857 96 : char *begin = *input;
858 : char *end;
859 96 : char attr = *begin;
860 :
861 96 : if (attr == '\0')
862 0 : ereport(ERROR,
863 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
864 : errmsg("malformed SCRAM message"),
865 : errdetail("Attribute expected, but found end of string.")));
866 :
867 : /*------
868 : * attr-val = ALPHA "=" value
869 : * ;; Generic syntax of any attribute sent
870 : * ;; by server or client
871 : *------
872 : */
873 96 : if (!((attr >= 'A' && attr <= 'Z') ||
874 96 : (attr >= 'a' && attr <= 'z')))
875 0 : ereport(ERROR,
876 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
877 : errmsg("malformed SCRAM message"),
878 : errdetail("Attribute expected, but found invalid character \"%s\".",
879 : sanitize_char(attr))));
880 96 : if (attr_p)
881 96 : *attr_p = attr;
882 96 : begin++;
883 :
884 96 : if (*begin != '=')
885 0 : ereport(ERROR,
886 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
887 : errmsg("malformed SCRAM message"),
888 : errdetail("Expected character \"=\" for attribute \"%c\".", attr)));
889 96 : begin++;
890 :
891 96 : end = begin;
892 4320 : while (*end && *end != ',')
893 4224 : end++;
894 :
895 96 : if (*end)
896 : {
897 0 : *end = '\0';
898 0 : *input = end + 1;
899 : }
900 : else
901 96 : *input = end;
902 :
903 96 : return begin;
904 : }
905 :
906 : /*
907 : * Read and parse the first message from client in the context of a SCRAM
908 : * authentication exchange message.
909 : *
910 : * At this stage, any errors will be reported directly with ereport(ERROR).
911 : */
912 : static void
913 96 : read_client_first_message(scram_state *state, const char *input)
914 : {
915 96 : char *p = pstrdup(input);
916 : char *channel_binding_type;
917 :
918 :
919 : /*------
920 : * The syntax for the client-first-message is: (RFC 5802)
921 : *
922 : * saslname = 1*(value-safe-char / "=2C" / "=3D")
923 : * ;; Conforms to <value>.
924 : *
925 : * authzid = "a=" saslname
926 : * ;; Protocol specific.
927 : *
928 : * cb-name = 1*(ALPHA / DIGIT / "." / "-")
929 : * ;; See RFC 5056, Section 7.
930 : * ;; E.g., "tls-server-end-point" or
931 : * ;; "tls-unique".
932 : *
933 : * gs2-cbind-flag = ("p=" cb-name) / "n" / "y"
934 : * ;; "n" -> client doesn't support channel binding.
935 : * ;; "y" -> client does support channel binding
936 : * ;; but thinks the server does not.
937 : * ;; "p" -> client requires channel binding.
938 : * ;; The selected channel binding follows "p=".
939 : *
940 : * gs2-header = gs2-cbind-flag "," [ authzid ] ","
941 : * ;; GS2 header for SCRAM
942 : * ;; (the actual GS2 header includes an optional
943 : * ;; flag to indicate that the GSS mechanism is not
944 : * ;; "standard", but since SCRAM is "standard", we
945 : * ;; don't include that flag).
946 : *
947 : * username = "n=" saslname
948 : * ;; Usernames are prepared using SASLprep.
949 : *
950 : * reserved-mext = "m=" 1*(value-char)
951 : * ;; Reserved for signaling mandatory extensions.
952 : * ;; The exact syntax will be defined in
953 : * ;; the future.
954 : *
955 : * nonce = "r=" c-nonce [s-nonce]
956 : * ;; Second part provided by server.
957 : *
958 : * c-nonce = printable
959 : *
960 : * client-first-message-bare =
961 : * [reserved-mext ","]
962 : * username "," nonce ["," extensions]
963 : *
964 : * client-first-message =
965 : * gs2-header client-first-message-bare
966 : *
967 : * For example:
968 : * n,,n=user,r=fyko+d2lbbFgONRv9qkxdawL
969 : *
970 : * The "n,," in the beginning means that the client doesn't support
971 : * channel binding, and no authzid is given. "n=user" is the username.
972 : * However, in PostgreSQL the username is sent in the startup packet, and
973 : * the username in the SCRAM exchange is ignored. libpq always sends it
974 : * as an empty string. The last part, "r=fyko+d2lbbFgONRv9qkxdawL" is
975 : * the client nonce.
976 : *------
977 : */
978 :
979 : /*
980 : * Read gs2-cbind-flag. (For details see also RFC 5802 Section 6 "Channel
981 : * Binding".)
982 : */
983 96 : state->cbind_flag = *p;
984 96 : switch (*p)
985 : {
986 86 : case 'n':
987 :
988 : /*
989 : * The client does not support channel binding or has simply
990 : * decided to not use it. In that case just let it go.
991 : */
992 86 : if (state->channel_binding_in_use)
993 0 : ereport(ERROR,
994 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
995 : errmsg("malformed SCRAM message"),
996 : errdetail("The client selected SCRAM-SHA-256-PLUS, but the SCRAM message does not include channel binding data.")));
997 :
998 86 : p++;
999 86 : if (*p != ',')
1000 0 : ereport(ERROR,
1001 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1002 : errmsg("malformed SCRAM message"),
1003 : errdetail("Comma expected, but found character \"%s\".",
1004 : sanitize_char(*p))));
1005 86 : p++;
1006 86 : break;
1007 0 : case 'y':
1008 :
1009 : /*
1010 : * The client supports channel binding and thinks that the server
1011 : * does not. In this case, the server must fail authentication if
1012 : * it supports channel binding.
1013 : */
1014 0 : if (state->channel_binding_in_use)
1015 0 : ereport(ERROR,
1016 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1017 : errmsg("malformed SCRAM message"),
1018 : errdetail("The client selected SCRAM-SHA-256-PLUS, but the SCRAM message does not include channel binding data.")));
1019 :
1020 : #ifdef USE_SSL
1021 0 : if (state->port->ssl_in_use)
1022 0 : ereport(ERROR,
1023 : (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
1024 : errmsg("SCRAM channel binding negotiation error"),
1025 : errdetail("The client supports SCRAM channel binding but thinks the server does not. "
1026 : "However, this server does support channel binding.")));
1027 : #endif
1028 0 : p++;
1029 0 : if (*p != ',')
1030 0 : ereport(ERROR,
1031 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1032 : errmsg("malformed SCRAM message"),
1033 : errdetail("Comma expected, but found character \"%s\".",
1034 : sanitize_char(*p))));
1035 0 : p++;
1036 0 : break;
1037 10 : case 'p':
1038 :
1039 : /*
1040 : * The client requires channel binding. Channel binding type
1041 : * follows, e.g., "p=tls-server-end-point".
1042 : */
1043 10 : if (!state->channel_binding_in_use)
1044 0 : ereport(ERROR,
1045 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1046 : errmsg("malformed SCRAM message"),
1047 : errdetail("The client selected SCRAM-SHA-256 without channel binding, but the SCRAM message includes channel binding data.")));
1048 :
1049 10 : channel_binding_type = read_attr_value(&p, 'p');
1050 :
1051 : /*
1052 : * The only channel binding type we support is
1053 : * tls-server-end-point.
1054 : */
1055 10 : if (strcmp(channel_binding_type, "tls-server-end-point") != 0)
1056 0 : ereport(ERROR,
1057 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1058 : errmsg("unsupported SCRAM channel-binding type \"%s\"",
1059 : sanitize_str(channel_binding_type))));
1060 10 : break;
1061 0 : default:
1062 0 : ereport(ERROR,
1063 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1064 : errmsg("malformed SCRAM message"),
1065 : errdetail("Unexpected channel-binding flag \"%s\".",
1066 : sanitize_char(*p))));
1067 : }
1068 :
1069 : /*
1070 : * Forbid optional authzid (authorization identity). We don't support it.
1071 : */
1072 96 : if (*p == 'a')
1073 0 : ereport(ERROR,
1074 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1075 : errmsg("client uses authorization identity, but it is not supported")));
1076 96 : if (*p != ',')
1077 0 : ereport(ERROR,
1078 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1079 : errmsg("malformed SCRAM message"),
1080 : errdetail("Unexpected attribute \"%s\" in client-first-message.",
1081 : sanitize_char(*p))));
1082 96 : p++;
1083 :
1084 96 : state->client_first_message_bare = pstrdup(p);
1085 :
1086 : /*
1087 : * Any mandatory extensions would go here. We don't support any.
1088 : *
1089 : * RFC 5802 specifies error code "e=extensions-not-supported" for this,
1090 : * but it can only be sent in the server-final message. We prefer to fail
1091 : * immediately (which the RFC also allows).
1092 : */
1093 96 : if (*p == 'm')
1094 0 : ereport(ERROR,
1095 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1096 : errmsg("client requires an unsupported SCRAM extension")));
1097 :
1098 : /*
1099 : * Read username. Note: this is ignored. We use the username from the
1100 : * startup message instead, still it is kept around if provided as it
1101 : * proves to be useful for debugging purposes.
1102 : */
1103 96 : state->client_username = read_attr_value(&p, 'n');
1104 :
1105 : /* read nonce and check that it is made of only printable characters */
1106 96 : state->client_nonce = read_attr_value(&p, 'r');
1107 96 : if (!is_scram_printable(state->client_nonce))
1108 0 : ereport(ERROR,
1109 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1110 : errmsg("non-printable characters in SCRAM nonce")));
1111 :
1112 : /*
1113 : * There can be any number of optional extensions after this. We don't
1114 : * support any extensions, so ignore them.
1115 : */
1116 96 : while (*p != '\0')
1117 0 : read_any_attr(&p, NULL);
1118 :
1119 : /* success! */
1120 96 : }
1121 :
1122 : /*
1123 : * Verify the final nonce contained in the last message received from
1124 : * client in an exchange.
1125 : */
1126 : static bool
1127 96 : verify_final_nonce(scram_state *state)
1128 : {
1129 96 : int client_nonce_len = strlen(state->client_nonce);
1130 96 : int server_nonce_len = strlen(state->server_nonce);
1131 96 : int final_nonce_len = strlen(state->client_final_nonce);
1132 :
1133 96 : if (final_nonce_len != client_nonce_len + server_nonce_len)
1134 0 : return false;
1135 96 : if (memcmp(state->client_final_nonce, state->client_nonce, client_nonce_len) != 0)
1136 0 : return false;
1137 96 : if (memcmp(state->client_final_nonce + client_nonce_len, state->server_nonce, server_nonce_len) != 0)
1138 0 : return false;
1139 :
1140 96 : return true;
1141 : }
1142 :
1143 : /*
1144 : * Verify the client proof contained in the last message received from
1145 : * client in an exchange. Returns true if the verification is a success,
1146 : * or false for a failure.
1147 : */
1148 : static bool
1149 96 : verify_client_proof(scram_state *state)
1150 : {
1151 : uint8 ClientSignature[SCRAM_MAX_KEY_LEN];
1152 : uint8 client_StoredKey[SCRAM_MAX_KEY_LEN];
1153 96 : pg_hmac_ctx *ctx = pg_hmac_create(state->hash_type);
1154 : int i;
1155 96 : const char *errstr = NULL;
1156 :
1157 : /*
1158 : * Calculate ClientSignature. Note that we don't log directly a failure
1159 : * here even when processing the calculations as this could involve a mock
1160 : * authentication.
1161 : */
1162 192 : if (pg_hmac_init(ctx, state->StoredKey, state->key_length) < 0 ||
1163 96 : pg_hmac_update(ctx,
1164 96 : (uint8 *) state->client_first_message_bare,
1165 192 : strlen(state->client_first_message_bare)) < 0 ||
1166 192 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1167 96 : pg_hmac_update(ctx,
1168 96 : (uint8 *) state->server_first_message,
1169 192 : strlen(state->server_first_message)) < 0 ||
1170 192 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1171 96 : pg_hmac_update(ctx,
1172 96 : (uint8 *) state->client_final_message_without_proof,
1173 192 : strlen(state->client_final_message_without_proof)) < 0 ||
1174 96 : pg_hmac_final(ctx, ClientSignature, state->key_length) < 0)
1175 : {
1176 0 : elog(ERROR, "could not calculate client signature: %s",
1177 : pg_hmac_error(ctx));
1178 : }
1179 :
1180 96 : pg_hmac_free(ctx);
1181 :
1182 : /* Extract the ClientKey that the client calculated from the proof */
1183 3168 : for (i = 0; i < state->key_length; i++)
1184 3072 : state->ClientKey[i] = state->ClientProof[i] ^ ClientSignature[i];
1185 :
1186 : /* Hash it one more time, and compare with StoredKey */
1187 96 : if (scram_H(state->ClientKey, state->hash_type, state->key_length,
1188 : client_StoredKey, &errstr) < 0)
1189 0 : elog(ERROR, "could not hash stored key: %s", errstr);
1190 :
1191 96 : if (memcmp(client_StoredKey, state->StoredKey, state->key_length) != 0)
1192 10 : return false;
1193 :
1194 86 : return true;
1195 : }
1196 :
1197 : /*
1198 : * Build the first server-side message sent to the client in a SCRAM
1199 : * communication exchange.
1200 : */
1201 : static char *
1202 96 : build_server_first_message(scram_state *state)
1203 : {
1204 : /*------
1205 : * The syntax for the server-first-message is: (RFC 5802)
1206 : *
1207 : * server-first-message =
1208 : * [reserved-mext ","] nonce "," salt ","
1209 : * iteration-count ["," extensions]
1210 : *
1211 : * nonce = "r=" c-nonce [s-nonce]
1212 : * ;; Second part provided by server.
1213 : *
1214 : * c-nonce = printable
1215 : *
1216 : * s-nonce = printable
1217 : *
1218 : * salt = "s=" base64
1219 : *
1220 : * iteration-count = "i=" posit-number
1221 : * ;; A positive number.
1222 : *
1223 : * Example:
1224 : *
1225 : * r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j,s=QSXCR+Q6sek8bf92,i=4096
1226 : *------
1227 : */
1228 :
1229 : /*
1230 : * Per the spec, the nonce may consist of any printable ASCII characters.
1231 : * For convenience, however, we don't use the whole range available,
1232 : * rather, we generate some random bytes, and base64 encode them.
1233 : */
1234 : char raw_nonce[SCRAM_RAW_NONCE_LEN];
1235 : int encoded_len;
1236 :
1237 96 : if (!pg_strong_random(raw_nonce, SCRAM_RAW_NONCE_LEN))
1238 0 : ereport(ERROR,
1239 : (errcode(ERRCODE_INTERNAL_ERROR),
1240 : errmsg("could not generate random nonce")));
1241 :
1242 96 : encoded_len = pg_b64_enc_len(SCRAM_RAW_NONCE_LEN);
1243 : /* don't forget the zero-terminator */
1244 96 : state->server_nonce = palloc(encoded_len + 1);
1245 96 : encoded_len = pg_b64_encode(raw_nonce, SCRAM_RAW_NONCE_LEN,
1246 : state->server_nonce, encoded_len);
1247 96 : if (encoded_len < 0)
1248 0 : ereport(ERROR,
1249 : (errcode(ERRCODE_INTERNAL_ERROR),
1250 : errmsg("could not encode random nonce")));
1251 96 : state->server_nonce[encoded_len] = '\0';
1252 :
1253 96 : state->server_first_message =
1254 96 : psprintf("r=%s%s,s=%s,i=%d",
1255 : state->client_nonce, state->server_nonce,
1256 : state->salt, state->iterations);
1257 :
1258 96 : return pstrdup(state->server_first_message);
1259 : }
1260 :
1261 :
1262 : /*
1263 : * Read and parse the final message received from client.
1264 : */
1265 : static void
1266 96 : read_client_final_message(scram_state *state, const char *input)
1267 : {
1268 : char attr;
1269 : char *channel_binding;
1270 : char *value;
1271 : char *begin,
1272 : *proof;
1273 : char *p;
1274 : char *client_proof;
1275 : int client_proof_len;
1276 :
1277 96 : begin = p = pstrdup(input);
1278 :
1279 : /*------
1280 : * The syntax for the server-first-message is: (RFC 5802)
1281 : *
1282 : * gs2-header = gs2-cbind-flag "," [ authzid ] ","
1283 : * ;; GS2 header for SCRAM
1284 : * ;; (the actual GS2 header includes an optional
1285 : * ;; flag to indicate that the GSS mechanism is not
1286 : * ;; "standard", but since SCRAM is "standard", we
1287 : * ;; don't include that flag).
1288 : *
1289 : * cbind-input = gs2-header [ cbind-data ]
1290 : * ;; cbind-data MUST be present for
1291 : * ;; gs2-cbind-flag of "p" and MUST be absent
1292 : * ;; for "y" or "n".
1293 : *
1294 : * channel-binding = "c=" base64
1295 : * ;; base64 encoding of cbind-input.
1296 : *
1297 : * proof = "p=" base64
1298 : *
1299 : * client-final-message-without-proof =
1300 : * channel-binding "," nonce [","
1301 : * extensions]
1302 : *
1303 : * client-final-message =
1304 : * client-final-message-without-proof "," proof
1305 : *------
1306 : */
1307 :
1308 : /*
1309 : * Read channel binding. This repeats the channel-binding flags and is
1310 : * then followed by the actual binding data depending on the type.
1311 : */
1312 96 : channel_binding = read_attr_value(&p, 'c');
1313 96 : if (state->channel_binding_in_use)
1314 : {
1315 : #ifdef USE_SSL
1316 10 : const char *cbind_data = NULL;
1317 10 : size_t cbind_data_len = 0;
1318 : size_t cbind_header_len;
1319 : char *cbind_input;
1320 : size_t cbind_input_len;
1321 : char *b64_message;
1322 : int b64_message_len;
1323 :
1324 : Assert(state->cbind_flag == 'p');
1325 :
1326 : /* Fetch hash data of server's SSL certificate */
1327 10 : cbind_data = be_tls_get_certificate_hash(state->port,
1328 : &cbind_data_len);
1329 :
1330 : /* should not happen */
1331 10 : if (cbind_data == NULL || cbind_data_len == 0)
1332 0 : elog(ERROR, "could not get server certificate hash");
1333 :
1334 10 : cbind_header_len = strlen("p=tls-server-end-point,,"); /* p=type,, */
1335 10 : cbind_input_len = cbind_header_len + cbind_data_len;
1336 10 : cbind_input = palloc(cbind_input_len);
1337 10 : snprintf(cbind_input, cbind_input_len, "p=tls-server-end-point,,");
1338 10 : memcpy(cbind_input + cbind_header_len, cbind_data, cbind_data_len);
1339 :
1340 10 : b64_message_len = pg_b64_enc_len(cbind_input_len);
1341 : /* don't forget the zero-terminator */
1342 10 : b64_message = palloc(b64_message_len + 1);
1343 10 : b64_message_len = pg_b64_encode(cbind_input, cbind_input_len,
1344 : b64_message, b64_message_len);
1345 10 : if (b64_message_len < 0)
1346 0 : elog(ERROR, "could not encode channel binding data");
1347 10 : b64_message[b64_message_len] = '\0';
1348 :
1349 : /*
1350 : * Compare the value sent by the client with the value expected by the
1351 : * server.
1352 : */
1353 10 : if (strcmp(channel_binding, b64_message) != 0)
1354 0 : ereport(ERROR,
1355 : (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
1356 : errmsg("SCRAM channel binding check failed")));
1357 : #else
1358 : /* shouldn't happen, because we checked this earlier already */
1359 : elog(ERROR, "channel binding not supported by this build");
1360 : #endif
1361 : }
1362 : else
1363 : {
1364 : /*
1365 : * If we are not using channel binding, the binding data is expected
1366 : * to always be "biws", which is "n,," base64-encoded, or "eSws",
1367 : * which is "y,,". We also have to check whether the flag is the same
1368 : * one that the client originally sent.
1369 : */
1370 86 : if (!(strcmp(channel_binding, "biws") == 0 && state->cbind_flag == 'n') &&
1371 0 : !(strcmp(channel_binding, "eSws") == 0 && state->cbind_flag == 'y'))
1372 0 : ereport(ERROR,
1373 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1374 : errmsg("unexpected SCRAM channel-binding attribute in client-final-message")));
1375 : }
1376 :
1377 96 : state->client_final_nonce = read_attr_value(&p, 'r');
1378 :
1379 : /* ignore optional extensions, read until we find "p" attribute */
1380 : do
1381 : {
1382 96 : proof = p - 1;
1383 96 : value = read_any_attr(&p, &attr);
1384 96 : } while (attr != 'p');
1385 :
1386 96 : client_proof_len = pg_b64_dec_len(strlen(value));
1387 96 : client_proof = palloc(client_proof_len);
1388 96 : if (pg_b64_decode(value, strlen(value), client_proof,
1389 96 : client_proof_len) != state->key_length)
1390 0 : ereport(ERROR,
1391 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1392 : errmsg("malformed SCRAM message"),
1393 : errdetail("Malformed proof in client-final-message.")));
1394 96 : memcpy(state->ClientProof, client_proof, state->key_length);
1395 96 : pfree(client_proof);
1396 :
1397 96 : if (*p != '\0')
1398 0 : ereport(ERROR,
1399 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1400 : errmsg("malformed SCRAM message"),
1401 : errdetail("Garbage found at the end of client-final-message.")));
1402 :
1403 96 : state->client_final_message_without_proof = palloc(proof - begin + 1);
1404 96 : memcpy(state->client_final_message_without_proof, input, proof - begin);
1405 96 : state->client_final_message_without_proof[proof - begin] = '\0';
1406 96 : }
1407 :
1408 : /*
1409 : * Build the final server-side message of an exchange.
1410 : */
1411 : static char *
1412 86 : build_server_final_message(scram_state *state)
1413 : {
1414 : uint8 ServerSignature[SCRAM_MAX_KEY_LEN];
1415 : char *server_signature_base64;
1416 : int siglen;
1417 86 : pg_hmac_ctx *ctx = pg_hmac_create(state->hash_type);
1418 :
1419 : /* calculate ServerSignature */
1420 172 : if (pg_hmac_init(ctx, state->ServerKey, state->key_length) < 0 ||
1421 86 : pg_hmac_update(ctx,
1422 86 : (uint8 *) state->client_first_message_bare,
1423 172 : strlen(state->client_first_message_bare)) < 0 ||
1424 172 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1425 86 : pg_hmac_update(ctx,
1426 86 : (uint8 *) state->server_first_message,
1427 172 : strlen(state->server_first_message)) < 0 ||
1428 172 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1429 86 : pg_hmac_update(ctx,
1430 86 : (uint8 *) state->client_final_message_without_proof,
1431 172 : strlen(state->client_final_message_without_proof)) < 0 ||
1432 86 : pg_hmac_final(ctx, ServerSignature, state->key_length) < 0)
1433 : {
1434 0 : elog(ERROR, "could not calculate server signature: %s",
1435 : pg_hmac_error(ctx));
1436 : }
1437 :
1438 86 : pg_hmac_free(ctx);
1439 :
1440 86 : siglen = pg_b64_enc_len(state->key_length);
1441 : /* don't forget the zero-terminator */
1442 86 : server_signature_base64 = palloc(siglen + 1);
1443 86 : siglen = pg_b64_encode((const char *) ServerSignature,
1444 : state->key_length, server_signature_base64,
1445 : siglen);
1446 86 : if (siglen < 0)
1447 0 : elog(ERROR, "could not encode server signature");
1448 86 : server_signature_base64[siglen] = '\0';
1449 :
1450 : /*------
1451 : * The syntax for the server-final-message is: (RFC 5802)
1452 : *
1453 : * verifier = "v=" base64
1454 : * ;; base-64 encoded ServerSignature.
1455 : *
1456 : * server-final-message = (server-error / verifier)
1457 : * ["," extensions]
1458 : *
1459 : *------
1460 : */
1461 86 : return psprintf("v=%s", server_signature_base64);
1462 : }
1463 :
1464 :
1465 : /*
1466 : * Deterministically generate salt for mock authentication, using a SHA256
1467 : * hash based on the username and a cluster-level secret key. Returns a
1468 : * pointer to a static buffer of size SCRAM_DEFAULT_SALT_LEN, or NULL.
1469 : */
1470 : static char *
1471 2 : scram_mock_salt(const char *username, pg_cryptohash_type hash_type,
1472 : int key_length)
1473 : {
1474 : pg_cryptohash_ctx *ctx;
1475 : static uint8 sha_digest[SCRAM_MAX_KEY_LEN];
1476 2 : char *mock_auth_nonce = GetMockAuthenticationNonce();
1477 :
1478 : /*
1479 : * Generate salt using a SHA256 hash of the username and the cluster's
1480 : * mock authentication nonce. (This works as long as the salt length is
1481 : * not larger than the SHA256 digest length. If the salt is smaller, the
1482 : * caller will just ignore the extra data.)
1483 : */
1484 : StaticAssertDecl(PG_SHA256_DIGEST_LENGTH >= SCRAM_DEFAULT_SALT_LEN,
1485 : "salt length greater than SHA256 digest length");
1486 :
1487 : /*
1488 : * This may be worth refreshing if support for more hash methods is\
1489 : * added.
1490 : */
1491 : Assert(hash_type == PG_SHA256);
1492 :
1493 2 : ctx = pg_cryptohash_create(hash_type);
1494 4 : if (pg_cryptohash_init(ctx) < 0 ||
1495 4 : pg_cryptohash_update(ctx, (uint8 *) username, strlen(username)) < 0 ||
1496 4 : pg_cryptohash_update(ctx, (uint8 *) mock_auth_nonce, MOCK_AUTH_NONCE_LEN) < 0 ||
1497 2 : pg_cryptohash_final(ctx, sha_digest, key_length) < 0)
1498 : {
1499 0 : pg_cryptohash_free(ctx);
1500 0 : return NULL;
1501 : }
1502 2 : pg_cryptohash_free(ctx);
1503 :
1504 2 : return (char *) sha_digest;
1505 : }
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